The present invention relates to cooling of solid state detectors in nuclear cameras and is particularly related to an apparatus that is adapted to cool the detectors and remove moisture. The present invention finds application in conjunction with nuclear medical diagnostic imaging systems and will be described with particular respect thereto.
Gamma cameras, also referred to as nuclear cameras, are often used to measure gamma radiation emitted by a body under examination. By measuring the energy and the location of the gamma ray emissions, an image representative of the gamma radiation emitted from the body under examination can be created. Gamma rays are produced by virtue of introducing one or more radionuclidies into a region of interest within a patient. These radionuclidies decay, thereby emitting gamma radiation characterized by photons having one or more characteristic energies.
Nuclear gamma cameras typically include one or more detector heads which receive the gamma radiation emanating from a patient. Many present design detector heads typically included a scintillation crystal which converts incident radiation to flashes of light. For a detector assembly utilizing the scintillation crystal, an array of photomultiplier tubes detects each scintillation event. The photomultiplier tubes are connected with position determining circuitry to ascertain the location of each received radiation event or scintillation, its energy, and other characteristics and produce the output signal which is indicative thereof. A collimator situated in front of the scintillation crystal is used to limit the field of view of the radiation detector and defines the detector's overall resolution and sensitivity (or efficiency). Typically, the detector head is housed in a radiation blocking material, such as a lead housing. The nuclear camera detector may be a planar nuclear gamma ray detector or a Single Photon Emission Computed Tomography (SPECT) system.
Recent development of the nuclear camera head includes a detector assembly which may be comprised of solid state detector (SSD) crystals of, for example, cadmium zinc telluride (CZT) or other suitable solid state devices or materials to directly provide electrical signals in response to detected radiation that are useful for generating diagnostic images. The solid state detector crystal array is connected with position determining circuitry to ascertain the location of each received radiation event, its energy, and other characteristics and produce the output signal which is indicative thereof.
It is known that cooling solid state detectors improves the system performance and reliability. However, cooling the systems below the dew point, particularly the dew point within the volume of the enclosed camera head, has been problematic. Cooling the CZT detectors below the dew point can allow moisture to condense on the crystals or other sensitive components within the detector head. This moisture creates a number of problems regarding performance and reliability. Cooling the detector components with forced air introduces dust and other contaminants while increasing the noise of the system.
Each detector head is connected to a gantry systems which rotates the detector head about a subject to obtain a complete data set. Rotation of a single detector head 360 degrees about a subject produces a complete data set. To reduce imaging time gamma cameras often contain two or more detector heads coupled to a single gantry system.
It is desirable to have a solid stated detector system that can be cooled to improve its performance and not compromise reliability due moisture to moisture and environmental conditions within the detector head. It is also desirable to cool the detector assembly without introducing dust or other contaminants into the system. Another desired feature it to reduce noise for the patient being imaged while providing cooling to the solid state detector system.